1. Field of the Invention
The present invention generally relates to a centrifugal dryer for removing surface moisture from pellets of resin material having a diameter generally ranging between approximately 0.015 to approximately 0.25 inches received from an underwater pelletizer. In one embodiment of the present invention, the dryer is constructed with smaller dimensions enabling it to effectively operate at low volume rates and be easily assembled and disassembled to facilitate cleaning and replacement or interchange of components with its overall size enabling it to be effectively used in small applications. In other embodiments of the present invention, the dryer is constructed with larger dimensions enabling it to effectively operate at high volume rates for use in commercial applications.
2. Description of the Prior Art
Centrifugal pellet dryers are well known and have been successfully used for many years to separate water from a water and pellet slurry and remove surface moisture from the pellets in order to provide relatively dry surfaces on the pellets for subsequent use. The following U.S. patents, owned by the assignee of this application, relate to centrifugal pellet dryers:
The following U.S. patents also relate to centrifugal pellet dryers:
The pellet dryers of the prior art do not have a sectional housing with upper and lower (base) sections being connected together by bolted external flanges for easy separation and access to the internal components. The prior art also fails to disclose the use of swing bolts to secure the housing sections together and does not disclose a depending extension on the upper housing below the flange thereon to engage the interior of the base section to provide a gasket free seal between the housing sections. The prior art also does not disclose a pellet dryer including a housing base section supported from a pivotal portion of the top of a water collecting tank to facilitate access to an underside of the base section and an inclined fines separation screen underlying the pivotal portion of the tank top in which a lower edge of the inclined fines separation screen discharges into a screened separation tray externally of the tank. In addition, the prior art does not disclose a centrifugal pellet dryer in which the rotor is supported from a single upper bearing and the lower end of the rotor is rotatably guided by an alignment bushing in the housing base section which is self-lubricating and cooled by the water of the water and pellet slurry thereby eliminating the need for providing a sealed bearing or other special device to protect a bottom bearing from the water.
Another feature not shown in the prior art is the use of a cylindrical screen in a centrifugal pellet dryer which telescopically engages a recessed edge of cup-shaped support members at the top and bottom ends of the screen and is supported by a pair of holding clips in the form of hooks to engage supporting pins on the upper cup-shaped support. Also, the prior art does not disclose the use of a lift device to assist in lifting and supporting major components away from the base section and to permit the supported components to be swung about a vertical axis away from alignment with the base section and tank to facilitate removal, cleaning and replacement of the dryer components. The prior art also fails to disclose a pellet dryer having an air circulating fan communicated with an upper end of the dryer for circulating air upwardly through the dryer for discharge laterally and upwardly to facilitate drying of the pellets. Further, the prior art does not disclose a structure on the underside of the pivotal portion of the water tank top to guide the fines and water toward an upper edge portion of the inclined fines screen.
The present invention is a centrifugal pellet dryer for removing surface moisture from resin pellets (approximately 0.015 to approximately 0.25 inches in diameter) and in one embodiment is specifically adapted for low volume use in laboratory applications and in other embodiments is specifically adapted for high volume use in commercial applications.
The centrifugal pellet dryer of this invention includes a sectional housing having separable sections that are quickly and easily connected together and disconnected from each other. The separable sections are preferably cylindrical top and base sections connected by mating external peripheral flanges that are bolted together by conventional bolts or swing bolts. The base section is mounted on a top wall of a water collecting or drain tank into which the water from the water and pellet slurry is drained, thereby eliminating the necessity of providing any piping system to remove the water from the dryer once separated from the pellets.
The centrifugal pellet dryer of this invention also includes a driven rotor that has a single supporting bearing at the upper end thereof with only an alignment bushing assembly at its lower end. A motor is preferably mounted atop a top plate to which the upper housing section is attached. The rotor supporting bearing is preferably mounted to the top plate and the alignment bushing assembly is preferably part of the lower or base section of the housing. This structure eliminates the necessity of providing a bottom bearing for the rotor and a sealing arrangement for the bottom bearing to preclude water from entering the bottom bearing thereby simplifying the structure. It also facilitates the easy separation and assembly of the top and base sections relative to each other.
Further, the centrifugal pellet dryer of this invention includes a lift and support device to lift the motor, rotor, top plate and upper housing section upwardly away from the lower or base section of the housing which allows the lifted components to be swung about a vertical axis away from the base section. This lifting, supporting and swinging structure may be in the form of a gas spring or a manually-actuated jacking device and enables removal of the upper section of the housing and screen to facilitate cleaning of the exposed bladed rotor as it remains connected to its driving shaft.
The centrifugal pellet dryer of this invention also preferably includes a cylindrical one-piece screen which is telescopically engaged with recessed end edges on top and bottom cup-like support structures. The screen also includes support hooks engaging the top support structure to removably support the screen within the top and base sections of the housing to facilitate assembly and disassembly of the screen in the dryer. Additionally, the tank includes a fines screen receiving water from the base section of the dryer for removing any solid material, partial pellets or fines which may be entrained in the water.
The pellet dryer of this invention also preferably includes a pivotal portion on the top of the water collecting or drain tank which supports the base section of the housing to provide access to an inclined fines screen in the tank, which screen has a lower edge extending outwardly of the tank to deposit separated material into a screened external tray.
The pellet dryer of this invention also includes a structure on the underside of the pivotal portion of the top of the water receiving tank to direct the water and fines toward an upper edge of the inclined fines screen.
The pellet dryer of the present invention also preferably includes a fan above the upper end of the housing and communicated with the interior thereof for circulating air upwardly through the housing and for discharge of the air laterally in relation to the housing.
Accordingly, it is an object of the present invention to provide a centrifugal pellet dryer for removing surface moisture from pelletized product which includes a sectional housing in which multiple sections are connected by external flanges that are bolted together to enable quick and easy assembly and disassembly of the housing.
Another object of the present invention is to provide a pellet dryer in which the rotor is rigid with a shaft supported by a single upper bearing and having an alignment bushing assembly guiding rotation of the lower end of the rotor thereby eliminating the need for a sealing device or special waterproof design to protect a bottom bearing from water within the dryer.
A further object of one form of this invention is to provide a centrifugal pellet dryer for laboratory applications in which the dryer is capable of operation at very low volume rates and is constructed of a relatively small overall size and of separable and replaceable components rendering it easily cleanable, repairable and otherwise well suited for laboratory or small applications.
An additional object of this invention is to provide a pellet dryer for commercial applications in other forms of the invention in which the dryer is capable of operation at very high volume rates and is constructed of a relatively larger size.
A still further object of the invention is to provide a lift for supporting and lifting the motor, the rotor and the upper housing section away from the housing base section when the dryer is being disassembled for repair and cleaning.
Still another object of the present invention is to provide a pellet dryer including a one-piece cylindrical screen having upper and lower edges telescopically engaged with recessed edges of top and bottom cup-like supports in the housing and support hooks engaging with support pins on the top support.
Yet another object of the present invention is to provide a centrifugal pellet dryer in which a base section of the housing is mounted directly on a top wall of the water drain tank so that water removed from the water and pellet slurry in the dryer can pass directly from the base section of the dryer housing into the water drain tank thereby eliminating the necessity of providing a piping system to drain water from the dryer.
It is a still further object of this invention to provide a pellet dryer in accordance with the preceding object in which the underside of the pivotal portion of the water drain tank includes a structure to direct water and fines toward the upper end portion of the screen.
An additional object of the invention is to provide a centrifugal pellet dryer in accordance with the preceding objects in which a fan is provided at the upper end of the housing for circulating air upwardly through the housing for discharge laterally of the dryer adjacent the upper end thereof.
A final object to be set forth herein is to provide a pellet dryer which will conform to conventional forms of manufacture, be of simple construction and easy to use so as to provide a dryer that will be economically feasible, long lasting and relatively trouble free in operation.
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming apart hereof, wherein like numerals refer to like parts throughout.